Gas sensor

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Quick Questions

Shade in the A or B circle for each question.

1. What does a gas sensor measure?

A The presence or concentration of a particular gas in the air

B The amount of light falling on it

2. Which device would use a gas sensor to protect people at home?

A A barcode scanner

B A carbon monoxide alarm

3. A gas sensor is an input device. True or false?

A True: it captures data from the environment and sends it to the processor

B False: it displays results to the user

4. Which is the best use of a gas sensor?

A Detecting a gas leak in a kitchen or factory

B Detecting when a door is opened by a magnet

5. What data does a gas sensor capture?

A Water level

B Gas concentration

Match the Pairs

Draw a line connecting each item on the left to its match on the right.

Left column		Right column
1gas sensor		AA gas sensor measures gas concentration, not temperature. A temperature sensor measures temperature.
2gas concentration		BThe data a gas sensor captures: how much of a particular gas is in the air
3A gas sensor in a carbon monoxide alarm detects a dangerous gas and triggers a warning		CA gas sensor is an input device. It detects gas in the air and does not release it.
4A breathalyser uses a gas sensor to measure the alcohol concentration in a person's breath		Dreading = gas_sensor.read("alcohol")
5A gas sensor is an output device that releases gas into the air		EAn input device that detects the presence or concentration of a particular gas in the air
6A gas sensor in a gas leak detector measures the temperature of the room		Fif gas_sensor >= safe_limit: sound_alarm()

Definitions

gas sensor

Fill in the Blanks

Complete each line of code by filling in the missing parts.

IF coLevel _ 50 THEN OUTPUT "Sound alarm" ENDIF

gasLevel ← _________.READ()

IF gasLevel > 30 THEN ______ "Gas leak!" ENDIF

IF alcoholLevel > limit ____ OUTPUT "Over the limit" ENDIF

REPEAT airLevel ← gasSensor.READ() UNTIL ________ > 50

Spot the Error

Shade in the letter of the line that contains an error.

Question 1

A INPUT co FROM gas_sensor

B IF co < 50 THEN

C OUTPUT "Alarm on"

D ENDIF

Question 2

A leak ← gas_sensor_value

B IF leak > 20 THEN

C valve ← OPEN

D ENDIF

Question 3

A alcohol ← gas_sensor_value

B limit ← 35

C IF alcohol > limit

D OUTPUT "Over the limit"

E ENDIF

Question 4

A WHILE TRUE

B level ← gas_sensor_value

C IF level > 100 THEN

D OUTPUT Poor air

E ENDIF

F ENDWHILE

Question 5

A DECLARE co : STRING

B co ← gas_sensor_value

C OUTPUT co

Answer Key

Gas sensor

Section A: Quick Questions

A — The presence or concentration of a particular gas in the air

B — A carbon monoxide alarm

A — True: it captures data from the environment and sends it to the processor

A — Detecting a gas leak in a kitchen or factory

B — Gas concentration

Section B: Match the Pairs

gas sensor → An input device that detects the presence or concentration of a particular gas in the air

gas concentration → The data a gas sensor captures: how much of a particular gas is in the air

A gas sensor in a carbon monoxide alarm detects a dangerous gas and triggers a warning → if gas_sensor >= safe_limit: sound_alarm()

A breathalyser uses a gas sensor to measure the alcohol concentration in a person's breath → reading = gas_sensor.read("alcohol")

A gas sensor is an output device that releases gas into the air → A gas sensor is an input device. It detects gas in the air and does not release it.

A gas sensor in a gas leak detector measures the temperature of the room → A gas sensor measures gas concentration, not temperature. A temperature sensor measures temperature.

Section C: Definitions

gas sensor — An input device that detects the presence or concentration of a particular gas in the air, e.g. in carbon monoxide alarms, gas leak detection, air quality checks and breathalysers.

Section D: Fill in the Blanks

IF coLevel > 50 THEN
   OUTPUT "Sound alarm"
ENDIF

gasLevel ← gasSensor.READ()

IF gasLevel > 30 THEN
   OUTPUT "Gas leak!"
ENDIF

IF alcoholLevel > limit THEN
   OUTPUT "Over the limit"
ENDIF

REPEAT
   airLevel ← gasSensor.READ()
UNTIL airLevel > 50

Section E: Spot the Error

B — The carbon monoxide alarm must sound when the gas level is too HIGH. The condition should be IF co > 50 THEN, not less than.

C — When the gas sensor detects a leak, the valve must be closed to stop the gas. It should be valve ← CLOSED.

C — An IF statement needs the keyword THEN after the condition. The line should be IF alcohol > limit THEN.

D — Text to be displayed must be written inside quotation marks. It should be OUTPUT "Poor air".

A — A gas sensor captures a number, the gas concentration, so the variable should be a numeric type such as INTEGER, not STRING.